The present disclosure relates to a display that emits light by utilizing organic electroluminescence (EL) phenomenon and to an electronic unit that includes the display.
As development of information and communications industry has been accelerated, a display device having high performance has been demanded. Specially, an organic EL device that has attracted attentions as a next generation display device has an advantage that the view angle is wide, the contrast is excellent, and the response time is short as a self-luminous display.
Materials used for a light emitting layer and the like forming the organic EL device are broadly classified into a low molecular material and a polymer material. In general, it is known that the low molecular material provides higher light emission efficiency and a longer life. In particular, performance of blue light emission in the case of using the low molecular material is high.
Further, in the case of using the low molecular material, in general, the organic film is formed by a dry method (evaporation method) such as a vacuum evaporation method. Meanwhile, in the case of using the polymer material, in general, the organic film is formed by a wet method (coating method) such as a spin coating method, an ink jet method, and a nozzle coating method or a printing method such as a flexo printing and offset printing.
The vacuum evaporation method has an advantage that a formation material of the organic thin film is not necessarily dissolved in a solvent, and a step of removing the solvent after forming the film is not necessitated. However, the vacuum evaporation method has disadvantages as follows. That is, separate coating by a metal mask is difficult, and facility manufacturing cost particularly in preparing a large panel is high. Therefore, the vacuum evaporation method is difficult to be applied to a large screen substrate, and is not suitable for mass production. Therefore, the coating method by which a large display screen area is comparatively easily realized has attracted attentions.
In the case where the coating method is used, however, in drying ink with which a space between pixels separated by a dividing wall is coated, the ink creeps up along the dividing wall resulting in wetting, and accordingly the aperture ratio is significantly lowered. Further, in the case where the pixel width is decreased to realize high resolution, it is difficult to coat a desired location with liquid droplets.
To resolve the foregoing disadvantages, for example, in Japanese Unexamined Patent Application Publication No. 2009-146885, as a method of suppressing film thickness unevenness caused by wetting and/or the like, a method of forming a dummy pixel region around an effective pixel region, and processing the shape of an insulating film in the vicinity of a lower electrode is disclosed. Further, as a method of obtaining a high-resolution display, for example, in Japanese Unexamined Patent Application Publication No. 2006-269253, a full-color display in which high resolution is achieved by forming a white pixel by coating the whole surface of a display region and using color filters of red (R), green (G), and blue (B) is disclosed.